【作者】 张雨；

【导师】 高超；

【作者基本信息】 上海交通大学 ， 材料学， 2009， 硕士

【摘要】 碳纳米管(CNTs)因其本身优异的电学、力学性能以及在纳米填充物、纳米器件、纳米生物技术等领域的潜在应用吸引了人们越来越多的关注。然而由于其本身溶解性比较差,而且缺少官能团极大地限制了碳纳米管在很多领域的应用.为了能够构建理想的结构,获得特定的性能,和应用在特殊的领域,因此对碳纳米管表面改性是具有极其重要意义的。到目前为止,在碳纳米管表面接枝聚合物刷主要有“接上去”和“接出来”两个方法。本文利用点击化学这一改性聚合物材料的强有力工具并结合逐层组装(Layer-by-Layer)、大分子引发剂法(Macroinitiator)、可逆加成-断裂链转移(RAFT)聚合、以及原子转移自由基聚合(ATRP),对碳纳米管功能化领域的“接上去”方式进行了推进,将多种功能聚合物和荧光分子以共价连接的方式接枝到碳纳米管表面。具体如下所述1.用点击化学和逐层组装法修饰碳纳米管提出了一种合成表面带有点击化学反应所需的炔键基团的碳纳米管的方法。然后分别用ATRP与RAFT聚合法合成了两种可点击的侧链基团全为叠氮基团与炔基的聚甲基丙烯酸-2-叠氮乙酯与聚甲基丙烯酸-2-丙炔酯。在Cu(I)/PMDETA催化下,将两种聚合物交替地以点击化学反应的形式接枝到碳纳米管表面。TGA、SEM和TEM测试表明可以通过控制两种聚合物的交替使用次数来控制接枝量并且管壁外聚合物层的厚度是均匀的。XPS和FTIR测试表明,在接枝三层聚合物后,碳纳米管的表面仍然有大量的剩余叠氮基团。然后,将单炔基罗丹明-B和端基为单炔基的聚苯乙烯以点击化学反应的形式接枝到碳纳米管表面从而合成了荧光碳纳米管和聚苯乙烯刷接枝的碳纳米管。结果表明,碳纳米管表面剩余的叠氮基团可进行进一步的点击化学反应,从而制得了基于碳纳米管的可进行点击化学反应的纳米器件。2.用点击化学和大分子引发剂法合成两亲性聚合物刷修饰的碳纳米管提出了一种新型的结合传统的“接上去”和“接出来”方法的多功能“双接枝”方法来改性碳纳米管和另一种合成表面带有点击化学反应所需的炔键基团的碳纳米管的方法。首先合成了一种新型的可点击大分子引发剂,侧链既含有可进行点击化学反应的叠氮基团,同时侧链又含有能引发APRP反应的烷基溴基团,即聚甲基丙烯酸-3-叠氮-2-(2-溴-2-甲基-丙酰氧)丙基酯。然后,通过点击化学反应,将可点击大分子引发剂接枝到带炔基的多壁／单壁碳纳米管表面,继而进行“接出来”方式的原位ATRP聚合和“接上去”方式的点击化学反应,将聚甲基丙烯酸正丁酯、聚乙二醇和聚苯乙烯接枝到碳纳米管上,制得了两亲性聚合物刷修饰的碳纳米管。TGA、FTIR、RAMAN、XPS、SEM和TEM测试表明,这种“双接枝”的方法可以简便地制备各种多功能聚合物刷修饰的碳纳米管,并且可以很好地控制接枝量。这种方法为制备两性的拥有双功能结构的聚合物刷以及化学修饰其他表面开辟了一条新道路。更多还原

【Abstract】 Carbon nanotubes (CNTs) as one of the most fascinating nanoobjects have attracted increasing interest, due to their unique electronic and mechanical properties and potential applications in the fields of nanofillers, nanodevices and nanobiotechnology. But their infusibility and lack of functional groups have limited the application in many fields. Modification of the surfaces of CNTs is of extreme importance, especially for the construction of desirable structures, gaining of tailor-made properties, and application of them in expected areas.Until now, two main strategies, "grafting onto" and "grafting from", have been presented and widely used to modify the surface of CNTs with polymers, giving rise to so-called polymer brushes. Taking advantage of the merits of click chemistry, a very powerful tool for post-modification of polymeric materials, via combination of living/controlled atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) polymerization, this thesis advanced the grafting onto approach, and grafted several different kinds of functional polymer and fluorescent molecular on the surfaces of CNTs. The details are as follows.1. Covalent layer-by-layer functionalization of multiwalled carbon nanotubes by click chemistryA new route for preparing the CNTs modified with alkyne groups which are needed for click reaction of Huisgen 1,3-dipolar cycloaddition between azides and alkynes. The clickable polymers of poly(2-azidoethyl methacrylate) and poly(propargyl methacrylate) were synthesized at first by atom transfer radical polymerization (ATRP) of 2-azidoethyl methacrylate and reverse addition-fragmentation chain transfer (RAFT) polymerization of propargyl methacrylate, respectively. The two polymers were then alternately coated on alkyne-modified multiwalled carbon nanotubes using Cu(I)/PMDETA as catalyst system. TGA, SEM and TEM measurements confirm that the quantity and thickness of the clicked polymer shell on MWNTs can be well controlled by adjusting the cycles or numbers of click reaction and the polymer shell is uniform and even. XPS and FTIR measurements showed that there was still a great amount of residual azido groups on the surfaces of the functionalized MWNTs after clicking three layers of polymers. Furthermore, alkyne-modified rhodamine B and monoalkyne-terminated polystyrene were subsequently used to functionalize the clickable polymer-grafted MWNTs, giving rise to fluorescent CNTs and CNT-based polystyrene brushes, respectively. It demonstrates that the residual azido groups on the surfaces of MWNTs are available for further click reaction with various functional molecules.2. Clickable macroinitiator strategy to build amphiphilic polymer brushes on carbon nanotubesA novel and versatile "Gemini-grafting" strategy to modify the surfaces of CNTs by a combination of conventional "grafting onto" and "grafting from" strategies and another new route for preparing the CNTs modified with alkyne groups are presented. A’clickable’macroinititor poly(3-azido-2-(2-bromo-2-methylpropanoyloxy)propyl methacrylate) (polyBrAzPMA) with alkyl bromo groups for initiating atom transfer radical polymerization (ATRP) and azido groups for click reaction was first synthesized by post-modification of poly(glycidyl methacrylate) with sodium azide followed by 2-bromoisobutyryl bromide. The’clickable’ macroinititor was clicked onto alkyne-containing multiwalled/singlewalled carbon nanotubes via Cu(I)-catalyzed’click’ reaction of Huisgen 1,3-dipolar cycloaddition between azides and alkynes, resulting in CNT-based clickable macroinitiator. Poly(n-butyl methacrylate), polystyrene and poly(ethylene glycol) were subsequently grown on CNTs via ATRP "grafting from" and click "grafting onto" approaches, affording CNT-supported amphiphilic polymer brushes. The functionalized CNTs were characterized by thermal gravimetric analysis (TGA), FTIR, Raman, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) measurements. All of the results demonstrated that it is feasible and facile to grow various multifunctional polymer brushes on CNTs by the clickable macroinitiator strategy, and the grafted polymer content can be well controlled. This versatile strategy can be readily extended to prepare other Janus/bifunctional polymer brushes, opening an avenue for building complex polymer architectures and tailoring surface properties.更多还原